1. Field of the Invention
The present invention relates to a fuel injecting apparatus for an internal combustion engine, and more particularly, to an exhaust gas assisted fuel injection system for an internal combustion engine in which exhaust gas re-circulated into a combustion chamber by an exhaust gas re-circulation (EGR) pipe is supplied to a fuel injector side to assist obtaining fine particles or vapor from injected fuel.
2. Description of the Related Art
In general, a system for supplying fuel into the combustion chamber adopts a PFI (Port Fuel Injection) system for injecting fuel to a suction port or a DI (Direct Injection) system for directly injecting fuel into the combustion chamber.
As the most prominent differences between the PFI system and the DI system, the PFI system carries out injection under pressure of about 3 bar while the DI system carries injection under pressure of 50 to 120 bar. Also, the PFI system is hardly influenced in injection time if a sufficient amount of time is provided for vaporization since injected fuel is introduced into the combustion chamber as mixed with air, whereas the DI system is strictly restricted in injection time for stratifying fuel within the combustion chamber.
In the DI system, since fuel is insufficiently vaporized, fuel may be burned in a droplet state or collide into a wall of a piston or the combustion chamber to produce smoke, and the NOx generating rate is fairly high since combustion takes place in a state that fuel efficiency is lowered and fuel is thin.
Also in the PFI system, fuel collides into the wall of the combustion chamber to mostly produce a liquid membrane thereby lowering fuel efficiency and deteriorating responsiveness of the engine while exerting a bad influence to exhaust gas also.
Therefore, an air assisted fuel injection system is used as an auxiliary means for the fine particle formation from fuel in the related art. The air assisted fuel injection system has promoted the fine particle formation of injected fuel by using the pressure difference before and behind a throttle. In this case, effect can be obtained in a low speed and low load range which have the large pressure difference, whereas effect can be hardly expected in a high speed range which has small pressure difference. Even though an auxiliary pump is used for obtaining the same effect in the high speed range, the auxiliary pump is not applied to an automobile in practice since power loss from pump actuation is too large.
Meanwhile, in order to reduce the amount of nitrogen oxide (NOx) in exhaust gas which is harmful to human bodies, the engine of the automobile is provided with an EGR system which re-circulates a portion of exhaust gas into a suction system to lower the maximum temperature in burning a mixture thereby restricting the generation of nitrogen oxide (NOx).
Such an EGR system comprises an EGR pipe for re-circulating a portion of exhaust gas released from an exhaust manifold to a suction manifold, an EGR valve installed in the middle of the EGR pipe for adjusting the amount of re-circulated exhaust gas, and a control unit for sending a control signal to the EGR valve according to operating conditions of the engine.
Also, a separate cooling system is installed in the middle of the EGR pipe at one side to reduce the temperature of circulated exhaust gas thereby restricting the generation of nitrogen oxide (NOx) in the maximum amount. However, installation of such a cooling system complicates the structure of the internal combustion engine and increases cost.
The present invention is proposed to solve the problems of the related art, and it is therefore an object of the invention to provide an exhaust gas assisted fuel injection system which introduces a portion of hot exhaust gas into a fuel injector to promote the fine particle formation and the vaporization of fuel thereby enhancing efficiency of fuel and re-circulates a portion of exhaust gas into a combustion chamber allowing the generation of nitrogen oxide to be restricted.
Also, it is another object of the invention to cool circulating exhaust gas by using heat of vaporization from injected fuel, by which inconvenience of additionally installing a cooling system for reducing the temperature of circulating exhaust gas and restricting the production of nitrogen oxide may be removed thereby enhancing convenience of manufacturing and reducing cost.
According to an embodiment of the invention to obtain the objects, it is provided an exhaust gas assisted fuel injection apparatus for an internal combustion engine, comprising: a fuel injector installed in a suction port for supplying fuel to a combustion chamber of the engine; an EGR line installed between one side of an exhaust manifold of the engine and the fuel injector so that a portion of exhaust gas released from the engine surrounds fuel injected from the fuel injector thereby promoting the fine particle formation and vaporization of injected fuel; an exhaust gas injection apparatus or EGR valve installed in one side of the EGR line for regulating exhaust gas within the EGR line; and a control unit for opening/shutting the exhaust gas injection apparatus or EGR valve according to operating conditions of the engine.